Re: quattro+rain

[Don Hoefer <hoefer@cary.eng.pko.dec.com>]

Aqua-planing or hydro-planing has to do with tire width (wider is
bad), water depth (deeper is bad), tire pressure (higher is good),
and tread depth (deeper is good).  The quattro system will have no
effect.  The quattro system will influence directional stability
however.

Hydro-plane speed is approximately 9/5 * tire pressure.  At 30 psi
this means that hydro-planing will take place at some speed over 54
MPH.

Hope this explains something.
Don Hoefer

>>>>	Today I drove my dad's S4 to the univeristy ,I drove to highway
and then the rain started heavily,I used highest wiper speed and turn on
fog lamp. I found that around 62 mph the car start to aquaplaning
(am I use the right word ?) I think 235/45 tyre play a major role here.
	I don't expect aquaplane in the quattro system,but it's ok ,the 
car still go straight while aquaplaning,doesn't like my MB which ride
on wide tyres (225/45)too,MB also aquaplane on this road when heavy rain,but
when it did ,it head seem to change direction,so AUDI is better in this 
respect.<<<<